A number of statistical cers have been developed to

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Unformatted text preview: mplexity of integrating life-cycle cost considerations
into the design and development process should not be
underestimated, but neither should the benefits, which
can be measured in terms of greater cost-effectiveness.
The existence of a rich set of potential life-cycle cost
trades makes this complexity even greater.
The Space Station Alpha Program provides
many examples of such potential trades. As one
example, consider the life-cycle cost effect of increasing
the mean time between failures (MTBF) of Alpha's
Orbital Replacement Units (ORUs). This is likely to
increase the acquisition cost, and may increase the
mass of the station. However, annual maintenance
hours and the weight of annual replacement spares will decline. The same station availability may be achieved
with fewer on-orbit spares, thus saving precious internal
volume used for spares storage. For ORUs external to
the station, the amount of extravehicular activity, with its
associated logistics support, will also decline. With such
complex interactions, it is difficult to know what the
optimum point is. At a minimum, the system engineer
must have the capability to assess the life-cycle cost of
each alternative. (See Appendix B.8 on the operations
and operations cost effects of ORU MTBF and Section
6.5 on Integrated Logistics Support.)
5.2.3 Cost Estimating The techniques used to estimate each life-cycle
cost component usually change as the project life cycle
proceeds. Methods and tools used to support budget
estimates and life-cycle cost trades in Phase A may not
be sufficiently detailed to support those activities during
Phase C/D. Further, as the project life cycle proceeds,
the requirements and the system design mature as well,
revealing greater detail in the Work Breakdown
Structure (WBS). This should enable the application of
cost estimating techniques at a greater resolution.
Three techniques are described below -parametric cost models, analogy, and grass-roots.
Typically, the choice of technique depends on the state
of information available...
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